Uva 11401 - Triangle Counting 解题报告(计数)
来源:互联网 发布:人工智能英语作文话题 编辑:程序博客网 时间:2024/05/21 17:24
Problem G
Triangle Counting
Input: Standard Input
Output: Standard Output
You are given n rods of length 1, 2…, n. You have to pick any 3 of them & build a triangle. How many distinct triangles can you make? Note that, two triangles will be considered different if they have at least 1 pair of arms with different length.
Input
The input for each case will have only a single positive integer n (3<=n<=1000000). The end of input will be indicated by a case with n<3. This case should not be processed.
Output
For each test case, print the number of distinct triangles you can make.
Sample Input Output for Sample Input
5
8
0
3
22
解题报告: 分析。假设现在最场边的长度为n。另外两条边的长度为a和b。由三角形的性质可以知道n-a<b<n。我们递推。如果a=1,那么该不等式无解;如果a=2,该不等式有1个解;直到a=n-2,不等式有n-2个解。那么一共有(n-2)(n-1)/2个解。当然,两条边除了相同相同长度,其他长度对都出现了两次,需要去重。相同长度的三角形数量为(n-1)/2。n长度以内的三角形是为最长边为3-n所有的三角形,所以预处理求和。代码如下:
#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long LL;const int maxn = 1000010;LL num[maxn];void init(){ for(int i=3;i<maxn;i++) num[i]=num[i-1]+((long long)(i-1)*(i-2)/2-(i-1)/2)/2;}int main(){ init(); int n; while(~scanf("%d",&n) && n>=3) printf("%lld\n", num[n]);}
- Uva 11401 - Triangle Counting 解题报告(计数)
- UVa 11401 - Triangle Counting//计数
- UVA 11401 - Triangle Counting(数论+计数问题)
- uva 11401 Triangle Counting 数三角形 (计数问题)
- 7_4_K题 Triangle Counting 题解 [uva 11401](计数)
- UVa 11401 Triangle Counting (组合计数)
- 【组合计数dp】UVA 11401Triangle Counting
- (解题报告)Uva-1225 --- Digit Counting
- UVA 11401 Triangle Counting——计数原理
- Uva 1640(计数) 解题报告
- UVA 11401 Triangle Counting
- Uva 11401 - Triangle Counting
- UVA 11401 Triangle Counting
- UVA 11401 - Triangle Counting
- UVA 11401 - Triangle Counting
- uva 11401 - Triangle Counting
- UVA - 11401 Triangle Counting
- UVA 11401 Triangle Counting
- POJ 2337 有向图的欧拉路径
- 无限级审核流程
- mybatis与ibatIS的区别
- cocos2d-x获得系统的语言
- Maximum Flow 练习:RookAttack,最大二分图匹配
- Uva 11401 - Triangle Counting 解题报告(计数)
- Arduino浮点数转换为字符串
- VB210-医学图像数据库的构建(SQL数据库) 原创新品,独家发布
- oracle手记
- java------用File类列出一个目录下的所有文件夹和文件
- *阵三角形java程序整理
- 题目1070:今年的第几天?
- js身份证验证代码(支持15位和18位身份证)
- linux c编程gets的替换函数